"""标志，有很多不同的事件会导致程序停止运行"""
prompt = "\nTell me something, and I will repeat it back to you:"
prompt += "\nEnter 'quit' to end the program. "
active = True

while active:
    message = input(prompt)
    # 所有导致程序停止运行的情况都将active设置为False
    if message == 'quit':
        active = False
    else:
        print(message)

"""break，退出循环"""

"""continue，跳过本次循环，继续下次循环"""